Apparatus for annealing strip



1952 E. J. SEABOLD APPARATUS FOR ANNEALING STRIP 5 Sheets-Sheet 2 FiledJune 27, 1946 n v .Ar

INVENTOR 1 Edward J Sea bo/d 12, 1952 E. J. SEABOLD 2,585,277

APPARATUS FOR ANNEALING STRIP Filed June 27, 1946 5 Sheets-Sheet :s

Feb. 12, 1952 E. J. SEABOLD 2,585,277

APPARATUS FOR ANNEALING STRIP Filed June 27, 1946 5 Sheets-Sheet 5\\5000OOOOOOO bO\\DOOOOOOO OO "I I l l 000000000000 I I 1 fig. 7

'TNvENToR Paiented Feb. 12, 1952 STATES PATENT OFFICE I 2,585,277APPARATUS FOR ANNEALING STRW Edward J. Seabold, Baltimore, Md., assignorto Drever Company, Philad tion of Pennsylvania elphia, Pa., a corpora-Application June 27, 1946, Serial No. 679,686

7 Claims. 3

periods which are unavoidable when annealing 1 coils, and a few suchinstallations have been made. Electric heating has usually beencontemplated by such proposals and incorporated in the actualinstallations The cost of electric accumulating surplus strip and meansfor permitting the strip'to be coiled after heating while in aprotective atmosphere, with provision for cutting the strip after a coilhas been completed and rejoining coils into a continuous strand forfinal cooling while still under a protective atmosphere. I also providecoile'r cars traveling around a closed path including stations at thedischarge end of the furnace and the entry end of the apparatus forcooling the strip rapidly in strand form.

A complete understanding of the invention may be obtained from thefollowing detailed description and explanation which refer to theheating is naturally greater thanthat of heating produced by thecombustion of fuel and this has limited the utilization of continuousannealing. Accordingly, it has been proposed heretofore increase thethermal efiiciency by causing the strip leaving a furnace after beingheated 2 to the desired maximum temperature, to give up heat to theentering strip which is at atmospheric temperature. The knownarrangements for this procedure, however, are not capable of achieving avery large recovery of heat.

I have invented a novel method and apparatus for annealing strip instrandform characterized by several advantages not realized before. In apreferred embodiment and prac- 1 ings,

accompanying drawings illustrating a preferred embodiment and practicethereof. In the draw- Figures 1A, 1B and 10 together constitute alargely diagrammatic view, partly in side elevationand partly inlongitudinal section showing one form of the apparatus;

' Figure 2 is a plan view of the entry looper; Figure 3, is a section onthe plane of line IIII1I of Figure 2;

Figure- 4 is a curve illustrating the variation in the temperature ofthe strip at various points in its travel through the apparatus;

tice, I provide a furnace withg'a heating section 'alongthe-plane ofline VIVI of Figure 5;

and a heat-exchange section 'and guide strip therethrough successivelyin strand form, in a plurality of vertical, up-and-down loops. The stripfirst enters the heat-exchange section and after passing through theheating section, it returns to the heat-exchange .section and-is broughtinto close proximity to the entering strip for a substantial period oftime. Specifically, the entering strip passes through severalup-and-down loops which extend between adjacent runs of the loopsthrough which the outgoing, heated strip travels. My method thuscomprises heating the entering strip first at a relatively low rate,then at a higher rate, and

Figure 5 is a view partly in plan and partly in horizontal section ofthe portion of the apparatus illustrated in Figure 10 which is a sectiontaken Figure 6 is a partial section, largely diagrammatic, taken alongthe plane of line VII-VII of Figure 5; a

Figure 7 is a partial section taken along the plane or line VIIIVlII ofFigure 5.

' Referring now in detail to the drawings and, for

the present, to Figures 1A, 1B and 1C, a coil of strip I 0 is fed fromone of two uncoilers I I through a welder l2 adapted to join the ends ofsuccessive coils into a continuous length. The strip then 1 passesaround a series of guide rolls i3, up over cooling the strip initiallyat a relatively low rate. Q

I subsequently cool the strip more rapidly. In one embodiment andpractice, I provide the furnace with a reheating chamber adapted toraise the temperature of the strip appreciably above the point to whichit is initially cooled. I 1

then coil the strip for furthercooling in an insulated enclosure afterwhich I uncoili the strip and cool it quickly to finaltemperaturefinstrand form. i

a looping roll Id and thence to a cut-out table having guide rolls atthe ends thereof. Th strip then passes'through a cleaning tank i6 and arinse tank I! passing about a plurality of vertically spaced guide rollsforming one or more loops.

From the rinse tank, the strip passes through a drier i8 and around apair of pulling pinch rolls i9.

. Th strip then passes to the entry looper 20.

1 The looper comprises an open fram 2! havin a My invention alsoincludes anovel looper for carriage 22 suspended therein for verticalmovement. The carriage 22 is provided with guide rolls 23 andcooperating guide rolls 24 are jour- I naled in the frame near the top.The strip p mechanism mounted on a platform ll at the top of the towerand including a torque motor 28 driving hoisting drums 21 through areduction gear 24. Cables 28 trained around the drums 21 and sheaves 88extend downwardly to the carriage.

The motor I8 is constantly energized and thus exerts a controllableupward force on the carriage. This force acts to partiallycounterbalance the weight of the carriag and its rolls but is notsuflicient to raise the carriage. This is effected only by thetensioning of the strip sufliciently to take up the surplus accumulatedin the looper. Whenever the carriage is raised as a result, the hoistingmechanism immediately overhauls the cables 29. I

From the entry looper 18, the strip passes around a pair of master pinchrolls II and over guide rolls in a trench l2 and into a furnaceindicated generally at I4. The furnace comprises a heating section 84and a heat-exchange section 85 subdivided by a cross wall'or baflle 31terminating short of the bottom of the furnace. The heating section hasbaille walls 38 terminating short of the top and bottom of the furnace.Electric resistance heaters 38 are mounted on the walls of the heatingsection and on the baille walls 38. The strip enters the furnace throughan opening 42 in the bottom thereof after passing between sealing rolls43.

Vertically spaced guide rolls 4. and 4| in the heat-exchange section 8!guide the entering strip through a plurality of up-and-down verticalpasses. These passes, as will be explained shortly, are parallel to aplurality of passes for the strip which haspassed through the heatingsection and is on its way out of the furnace. The entering strip isthereby heated at a relatively low rate, by radiation from th previouslyheated portions of the strip. Guide rolls 44 adjacent the top and bottomof the heating section 34 guide the preheated strip through a pluralityof up-anddown passes between the baille walls 38. In this portion of itstravel, the strip is further heated by direct radiation from the heaters39. The heaters in the last pass, however, are adjusted merely to supplythe heat losses through the walls without raising the temperature of thstrip, thereby afiordin an opportunity for the heat to soak through thematerial so that all portions of the latter will beat a uniformtemperature.

From the last pass in th'eheating section, the strip passes over spacedguide r'olls 45 above the upper guide rolls 44 and then travels oververtically spaced guide rolls 48 and 41 so disposed in the heat-exchangesections that the outgoing strip, as previously-stated, willclosely'parallel the several runs of the incoming strip between theguide rolls 48 and 4|. It will be evident from the drawings that theguide rolls 48 and 4| for the entering strip and the guide rolls 48 and41 for the strip leaving the furnace cause the strip to pass throughmutually interfltting up-and-down loops whereby a good opportunity isafforded for absorption of heat by the entering strip from that 4 whichhas already passed through the heating section. This. effects arelatively slow cooling of the strip leaving the furnace, concurrentlywith the relatively slow heating of the entering strip.

I am able to produce material having greater ductility by heating itslightly and coiling it under a protective atmosphere for furthercooling at a very low rate in coiled form. The strip is then uncoiledand finally cooled at a higher rate in strand form, under a protectiveatmosphere.

On leaving the heat-exchange section, the strip enters a reheatingsection 88 provided, like the heating section 34, with radiant heaters88. The section 86 has upper and lower guide rolls 81 and 88 andincludes two vertical passes. After traversing both these passes, thestrip passes over exit guide rolls 48' and thence around a series ofstaggered flexing and drag rolls 69 enclosed within a thermallyinsulated chamber 10.

A plurality of coiler cars 1| are adapted to travel around a closedtrack 12 including turntables 13 and 14. The turntable 13 is locatedadjacent the chamber 10 and the turntable 14 adjacent a cooling tower15. Each coiler car includes a thermally insulated enclosure 18 mountedon wheels and having a coiling mandrel 11 journaled therein. An innercover 18 is provided for maintaining an atmosphere of protective gasaround a coil of strip on the mandrel 11. A removable cover 19 isdisposed on the enclosure 18 while coiling strip on the mandrel. A drivemechanism indicated at adjacent the turntable 13 is adapted to becoupled to the mandrel 11 when it is desired to coil strip thereon.

An access gate 8| is provided in a neck 82 extending outwardly from thechamber 10 and having a seal 83 therein. A similar neck 84 extendingfrom the enclosure 10 is adapted to engage the gate 8| and has a seal 85therein. The gate is preferably water-cooled. The mandrel 11 has alength of strip permanently secured thereto to which the end of thestrip emerging from the chamber 10 is adapted to be welded by a welder Won opening of the access gate 8| after the seals 88 and 85 have beenclosed. When the connection has been made, the gate is reclosed and theseals opened, whereupon the strip which has been through the furnace maybe coiled by driving the mandrel 11, the strip being fully protectedagainst atmospheric oxidation at all times. When a full coil has beenwound on the mandrel 11, the seals 83 and 85 are again closed. Theportion of strip within the gate 8| may then be quickly cooled byspecial connections for circulating protective gas therethrough. Thegate 8| is then opened and the completed coil is severed from thesucceeding portion of the continuous length of strip. Preferably theseverance is effected at the welded joints between successive lengthsmade by the welder l2. After a coil has been wound on the mandrel, thecover 18 is removed from the enclosure 18 and the car 1| is advancedcounterclockwise along the track 12 and an empty car is brought intocoiling position.

If desired, radiant heaters 89 may be mounted adjacent the bottom of thecoiler cars to provide controlled cooling of the coils. The current forthese heaters and the protective atmosphere for the inner cover aresupplied by radial connections from slip rings indicateddiagrammatically at 88 and acentral supply pipe 81. A connection 81aextends from the pipe 81 to a source of gas suitable for the atmospheresurrounding the coils. A. connection 81b extends from the slip rings toa suitable source of current. The radial connection for the currentleads includes a flexible loop 88 and the connection for supplying gasto the inner cover includes piping 89 and a telescoping connection 90.

As shown in Figures 5 and 1C, a plurality of coiler cars are employedand they advance sl0wly around the track 12 in succession after havingcoils wound thereon. The number of cars and the length of the track, ofcourse, will be such as to provide the desired period of furnace coolingfor the coils so that, by the time a car has reached the turntable M,its coil will have cooled to a temperature of around 900 after whichmore rapid cooling may be effected in the tower 15. The latter, as shownin Figure 7, is provided with an access gate SI and a seal 92 similar tothose of the chamber 10. Thus, when a car has been properly positioned,relative to the tower 15, the end of the coil projecting through theseal 85 may be connected as by welding to the end of a length of stripalready started through the tower 15 after which the gate 9| may beclosed and the seals 92 and 85 opened so that the strip may be uncoiledand passed through the tower in strand form. When the coil has beenunwound and severed from the connection length secured to the mandrel,the car is returned to a position adjacent the chamber 10 by aconnecting track 12a.

The tower 15 is provided with upper and lower rolls 93 and 96 aroundwhich the strip passes in a plurality of up-and-down loops. Banks ofcooling coils 95 are disposed between the loops and have watercirculated therethrough in order to cool the strip rapidly. An extension96 from the tower is provided with a plurality of air-cooled rolls 9'!and water-cooled rolls 91a around which the strip passes for furthercooling. On leaving the extension 95, the strip passes between sealingrolls 98 and around a guide roll 99 in a quench tank I00. The strip thenpassesupwardly between wringer rolls l0, through drying chutes I02 andfinally around a standof coiler pinch rolls I03 and onto a coiler I06.

Figure 4 illustrates graphically the variation in the temperature of apoint on strip from .040 to .075" thick being processed in accordancewith a typical example of the modified practice of the invention,although the exact values of temperature are merely for illustration andmay vary materially. The strip is first heated from atmospherictemperature to a maximum of about 1700 as indicated by portion g of thecurve of Figure 4. This heating is actually accomplished in two steps,at diilerent rates, but this is not shown in Figure 4 because of thesmall scale employed on the horizontal axis. The material is heated fromroom temperature in passing through the heat-exchange section and as thestrip passes through the heating section of the furnace, its temperaturerises more rapidly. The strip is then held at the maximum temperaturefor a short time as indicated at h and is next cooled at a relativelyslow rate to a temperature of between 1000 and l100 as it passes throughthe heatexchange section of the furnace. This is indicated by portion 7'of the curve. Next the strip passes through the reheating section 66 andits temperature is raised to about 1200" as indicated by portion is ofthe curve. After being coiled, a very slow or furnace cooling of thestrip occurs as indicated by the portion m of the curve to a temperatureof between 800 and 900". It will be noted that in this portion of thecurve, the horizontal scale has been compressed. After traveling aroundthe track 12 on one of the coiler cars, and being entered into thecooling tower 15, the strip has its temperature reduced rapidly to about300 as shown by portion 12 of the curve of Figure 4 and is finallyquenched as indicated by portion 0 of the curve.

If it is desired to produce bright-annealed strip, the furnace chamberand cooling towers must be supplied with an atmosphere of non-oxidizinggas. A suitable atmosphere may be obtained by burning any clean fuel gaswith an insufficient supply of air, cooling and dehydrating it. The gasis preferably introduced into the furnace in the heating section andflows under a slight positive pressure toward the cooling towers. Thegas, however, may be first passed through the quench tank above thesurface of the water to remove any vapor therefrom.

It will be apparent that the method and apparatus described above arecharacterized by numerous advantages. Among these are the speed ofprocessing which enables finished material to be shipped soon after itis cold rolled as is now being demanded increasingly by consumers, theproduction of material having good physical properties andmicro-structure in substantial amounts, 1. e., up to 15 tons per hour.at an overall cost no greater than that of the conventional batchannealing. In respect to cost, a special advantage is the Savingresulting from the fact that the cleaning step is combined with theannealing. It will be appreciated that this avoids the extra handlingnecessary when the cleaning operation is conducted separately, as wellas the cost of a separate cleaning line. By heating the material insingle strand. more accurate control of the time-temperature cycle isobtained as well as a greater flexibility in the heat treatment. Thedesired relief of strain and refinement of grain can readily beaccomplished. The maximum temperature is easily controlled as well asthe soaking stage and successive cooling stages. Processing in strandform also produces material which is more nearly uniform in annealingcharacteristics throughout the length of the strip. One factor in theeconomy achieved by the invention is the fact that it permits therecovery of about 50% of the heat imparted thereto. The flexibilityresults from various combinations of time and temperature which may beobtained by changes in the speed of travel of the strip and the easewith which the heat energy delivered to the strip may be controlled.

The procedure described hereinabove provides an improved annealing cyclebecause of the relatively slow heating and cooling which occurs at thebeginning of the heating and cooling stages, respectively. Slow initialcooling of the material from its maximum temperature to about 900 F. isparticularly desirable. Below that temperature, the strip may be cooledmore rapidly for efilcient operation. The final cooling by a waterquench permits the strip to be temper-rolled immediately.

In addition, the practice has the advantage of very slow coolingcharacteristic of batch annealing without the limitation to slow heatingwhich is also characteristic thereof as well as wide variations in thetime at which various portions of the coil are held at the maximumtemperature. The very slow cooling thus obtained promotes completespheroidization giving a product having extremely good ductility. Thereheating step relieves any internal strain produced by the initial 7cooling but does not cause grain growth, thereby preserving the smallgrain size produced by the initial cooling.

It will be evident that the invention is well.

mdapted to automatic control. The details thereof are not shown,however, to suit the needs of particular installations.

Although I have illustrated and described but a preferred embodiment andpractice of the invention, it will be recognized that changes in theprocedure and apparatus disclosed may be made without departing from thespirit of the invention or the scope of the appended claims.

I claim:

1. In strip annealing apparatus, in combination, a heating furnace forheating strip in strand form, said furnace having an outlet for saidstrand, a movable enclosure adapted to bemoved into registry with saidoutlet, means for coiling said strand within said enclosure, a coolingtower adapted to cool strip in strand form having an inlet for saidstrand, means for moving said movable enclosure along a closed trackcircuit after a strand has been coiled therein out of registry with saidfurnace outlet and into registrywith said tower inlet, means foruncoiling said coil in said enclosure and passing it through said inletto cool said strand and means for returning said movable closure intoregistry with said furnace outlet, whereby rapid heating, temperatureholding and relatively rapid cooling are obtained.

2. In strip annealing apparatus, in combination, a loop heatingfurnacefor heating strip in strand form, said furnace having an outlet for saidstrand, a movable enclosure adapted to be moved into registry with saidoutlet, means for coiling said strand within said enclosure, 9. loopcooling tower adapted to cool strip in strand form having an inlet forsaid strand, meansfor moving said movable enclosure along a closed trackcircuit after a strand has been coiled therein out of registry with saidfurnace outlet and into registry with said tower inlet, means foruncoiling said coil in said enclosure and passing it through said inletto cool said strand, means for supplying protective gas to said furnace,en-' closure and tower, sealing means for the respec-' tive passagesbetween said furnace and said enclosure and between said enclosure andsaid tower during movement of strip therebetween, and means forreturning said movable closure into registry with said furnace outlet,whereby rapid heating, temperature holding and relatively rapid coolingare obtained in a continuously protected atmosphere.

3. In strip annealing apparatus,- in combination, a heating furnace forheating strip in strand form, said furnace having an outlet for saidstrand, a plurality of insulated coiler cars adapted to be movedsuccessively into registry with said outlet, means for successivelypulling strands from said furnace and coiling them respectively withinsaid coiler cars, a cooling tower adapted to cool a strip in strand formhaving an inlet for said strand, means for moving said coiler carssuccessively into registry with said tower inlet, a closed circuit trackextending between said furnace and said tower and adapted to accommodatea predetermined number of said coiler cars, said track extending alongone path from said furnace to said tower and along another return pathfrom said tower to said furnace, and means for-uncoiling said coil ineach of said coiler cars when said cars are respectively since they maybe varied- 8 in registry with said tower inlet to pass the strip thereinin strand form through said inlet to cool moved to bring said neck intoregistry with said outlet, strip sealing means respectively on saidoutlet and said neck, an access gate extending between said stripsealing means when in said registry, common means for pulling saidstrand from said furnace and coiling it within said coiler car, a welderadapted to weld the leading end of said strand to said coiling stripwhen said access gate is open and said strip sealing means are closed,said access gate being adapted to be closed after said welder iswithdrawn, said strip sealing means being adapted to be opened when saidaccess gate is closed to permit coilingof said strand in said coilercar, a cooling tower adapted to cool a stripin strand form having aninlet for said strand, means fOr moving said loaded coiler car to bringsaid neck into registry with said inlet, strip sealing means on saidinlet, an access gate extending between said respective strip sealingmeans when in said last-mentioned registry, said welder being adapted toweld the outer end of said coiler strand in said coiler car to thefollowing end of a strand passing through said tower. when saidlast-mentioned access gate is open and said respective strip sealingmeans are closed, and means for uncoiling said strand when said welderis withdrawn to cool said strand, whereby strand heating and coolingtake place in continuous strip processing with intermediate coiltemperature holding in an annealing operation.

5; In strip sealing apparatus, in combination, a loop heating furnacefor heating strip in strand form, said furnace having an outlet for saidstrand, strip sealing means at said outlet, at least two closed coilercars adapted to coil said strand therein and transport the same, eachsaid car having a neck adapted to be moved into registry with saidoutlet, strip sealing means at said neck, a loop cooling tower adaptedto cool a strip in strand form having an inlet for said strand, stripsealing means at said inlet, means for'moving each of said cars to movethe neck th'ereof out of registry with said' outlet and into registry'with'said inlet, access gates adjacent said outlet and inlet adapted tobridge the space between said respective strip sealing means whentheyare in respective registry, welding means for said strand adapted to beintroduced through said respective access gates when said respectivestrip sealing means are closed, a substantially closed track circuitextending between said furnace and said tower along which said cars aremoved, and centrally positioned means for supplying protective gas tosaid cars during movement, whereby strand heating and cooling takesplace in substantially continuous strip processing with intermediatecoil temperature holding in an annealing operation with a continuouslyprotective atmosphere.

6. In strip annealing apparatus, in combination, a strand heatingfurnace having an outlet, a gas seal adjacent said outlet, an accessgate 9 adjacent said seal, a coiler car having a common inlet and outletthereto, a gas seal on said coiler car adjacent said common inlet andoutlet, said coiler car movable into and out of position with said sealsand said access gate in registry to provide a short direct passage forsaid strand into said coiler car, a mandrel within said coiler car, andmeans for turning said mandrel to pull said strand from said furnace andcoil it within said coiler car before opening said access gate to seversaid strand and move said car out of registry with said furnace outlet.

'7. In strip annealing apparatus, in combination, a strand heatingfurnace having an outlet, a gas seal adjacent said outlet, an accessgate adjacent said seal, a coiler car having a common inlet and outletthereto, a gas seal on said coiler car adjacent said common inlet andoutlet, said coiler car movable into and out of position with said sealsand said access gate in registry to provide a short direct passage forsaid strand into said coiler car, a mandrel within said coiler car,means for turning said mandrel to pull said strand from said furnace andcoil it within said coiler car before opening said access gate to seversaid strand and move said car out of registry with said furnace outlet,a strand cooling enclosure having an inlet, a gas seal adjacent saidinlet, an access gate adjacent said last-mentioned EDWARD J. SEABOLD.

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